How do you compare prices with different pack sizes?

The comparator converts every pack to a common base unit — grams for weight, millilitres for volume, or a single item for count — then divides the price by that base amount. Because a 500 g bag and a 1.5 kg bag are both reduced to a price per gram, you can compare them directly even though the packs look nothing alike. The result is shown in a readable denominator such as per 100 g, per litre or per item.

What does price per unit actually mean?

Price per unit is the cost of one standard amount of a product — for example the cost of 100 grams, one litre, or one item — rather than the cost of the whole pack. It is the only fair way to compare value, because a bigger pack with a higher sticker price is often cheaper per unit than a small pack that looks like a bargain.

Can I compare weight against volume?

No, and the tool deliberately stops you. A price per kilogram and a price per litre measure different physical quantities, so ranking them together would be meaningless. If you mix units the comparator ranks and charts only the most common measurement type and shows a warning, so the verdict always compares like with like.

How do I handle a multi-buy or 3-for-2 offer?

Put the total price you actually pay for the whole deal in the Price field, the size of a single item in Amount, and the number of items you receive in Packs. The tool multiplies the quantity out, so a 3-for-2 on 400 g jars is correctly costed across the full 1,200 g you take home, not just one jar.

Is the cheapest unit price always the best buy?

Usually, but not always. The lowest unit price is the best value for money, yet the bigger pack that wins on unit price also costs more up front and can go to waste if you cannot use it in time. Use the unit price to judge value, then sanity-check it against your budget and how much you will realistically consume.

Is my data private and is this free?

Completely private and free. Every calculation runs in your browser using JavaScript — no prices, product names or figures are ever uploaded to a server. Your rows are saved only in this browser via local storage so they are still there when you come back, and you can clear them at any time.

Unit Price Comparator

A unit price comparator that turns confusing supermarket pricing into a single, fair number: the cost per kilogram, per litre or per item. Shops love to make value hard to judge — a small pack on offer can look cheaper than a big bag that is actually far better value per gram. This tool strips away the packaging and tells you which product genuinely costs less for the same amount, ranking every option and highlighting the winner in green.

It is built for real shopping decisions. Add a row for each product, type the pack price and the pack size, choose the unit, and the comparator instantly normalises everything to a common base and shows the price in a readable denominator. It handles multi-buy deals, mixes of pack sizes, and even warns you when you accidentally try to compare weight against volume — because a price per kilogram and a price per litre can never be ranked against each other honestly.

How it works

Every product you enter is converted to a single base unit. Weights collapse to grams, volumes to millilitres, and counted goods to a single item. The pack price is then divided by the total base amount to give a raw price-per-base-unit, which the tool re-expresses in something human — per 100 g, per litre, or per item — so the figures are easy to read and compare. Multi-buy deals are handled by multiplying the per-pack quantity by the number of packs in the offer, so a 6-pack or a 3-for-2 is costed across everything you actually take home.

Once at least two comparable products are entered, the comparator sorts them cheapest-first, highlights the best value, reports how much cheaper it is than the dearest option as a percentage, and draws a horizontal bar chart so the gap is obvious at a glance. You can export the whole comparison to CSV for a shopping list or a spreadsheet, and your rows are saved in your browser so they are still there next time.

Example

Imagine three options for the same coffee. A 250 g jar at 3.20, a 500 g jar at 5.40, and a 3-for-2 deal on the 250 g jars priced at 6.40 for three. Entering each as a row — with the deal as price 6.40, amount 250 g, packs 3 — the comparator reduces them to roughly 1.28 per 100 g, 1.08 per 100 g, and 0.85 per 100 g respectively.

Option	Pack	Price	Per 100 g
Small jar	250 g	3.20	1.28
Big jar	500 g	5.40	1.08
3-for-2 deal	3 × 250 g	6.40	0.85

The 3-for-2 deal wins — about 34% cheaper per 100 g than the small jar that looked like the obvious single purchase. Every figure is calculated in your browser, and nothing is ever uploaded or stored on a server.